Masonry cutting tool



Oct. 4, 1966 .J D. DITSON 3,276,820

MASONRY CUTTING TOOL Filed March 29, 1965 2 Sheets-Sheet l JNVENTOR. J. D. D/ TSO/V BY W wrrm ATTORNEY Oct. 4, 1966 J. D. DITSON 3,276,820

MASONRY CUTTING TOOL Filed March 29, 1963 2 Sheets-Sheet 2 FIG. /0

INVENTGR. J. 0. 0/75 O/V ATTORNEY United States Patent 3,276,820 MASONRY CUTTING TOOL J. D. Ditson, Asbury, N.J., assignor to Ingersoll-Rand Company, New York, N.Y., a corporation of New Jersey Filed Mar. 29, 1963, Ser. No. 269,053 4 Claims. (Cl. 299-94) This invention relates to percussively-operated tools for drilling and breaking concrete and similar materials and particularly to drill steels or bits known as moil points used with paving breakers.

Conventional moil points have an undesirable tendency to stick in concrete when driven to a depth wherein the cutting end portion of the tool is well buried. This sticking is objectionable for it makes the operation of a paving breaker much more laborious than it would be if the moil points did not stick. In many cases, this sticking tendency is caused by dust and cuttings accumulating on the Sides of the moil point near corners or discontinuous surfaces extending laterally across the tool. Such corners are usually formed where the cutting portion of the tool joins the main body of the tool.

The principal object of this invention is to eliminate the foregoing disadvantage and to provide a percussivelyoperated tool which greatly reduces and minimizes the sticking" problem.

Another important object of this invention is to provide a method for making a novel and highly desirable percussively-operated tool for drilling and breaking concrete and similar materials.

Other important objects of this invention include the following: to provide a moil point having longitudinal surfaces extending smoothly from the point of the tool rearwardly along the main body of the tool for providing smooth and continuous troughs along which cuttings will flow without collecting at any point along the tool to cause the tool to stick in the hole being drilled; and to provide a more economical method for making a moil point having superior operating characteristics.

Briefly, the foregoing objects are attained in a method including the following steps: starting with an elongated bar of polygonal cross section; heating an intermediate portion of the bar under controlled temperature conditions; and axially pulling apart the two portions of the bar on the opposite sides of the heated portion to cause the heated portion to attenuate and ultimately separate as a pair of pointed portions. During the attenuation, the original sides of the polygonal cross section are drawn smoothly forward to the tips where the pointed portions separate and form substantially concave troughs or channels extending rearward from the tip of each pointed portion.

This invention is described in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a moil point made according to the invention and having portions broken away;

FIG. 2 is another perspective view of the tool shown in FIG. I looking substantially at the pointed end of the tool;

FIGS. 3 to 7 are sections taken along corresponding lines in FIG. 1 and being reduced in scale;

FIG. 8 is a schematic elevational view of an apparatus used in making the novel tool and showing a tool blank mounted in the apparatus prior to being attenuated;

FIG. 9 is a schematic elevational view showing the tool blank of FIG. 8 in a partly attenuated condition; and

FIG. 10 is a schematic elevational view showing the tool blank at the finish of attenuation.

The tool embodiment illustrated in the drawings is a moil point 1 for use in a paving breaker and conventionally includes an elongated body, also designated 1,

3,276,820 Patented Oct. 4, 1966 having a shank 2 at its rear end adapted to fit in the chuck of a conventional paving breaker. The shank 2 is of hexagonal cross section and includes an enlarged collar 3 at its front end.

The elongated body 1 further includes an intermediate elongated portion 4 projecting forward of the collar 3. In the embodiment shown in the drawing, the intermediate portion 4 is of hexagonal cross section and is formed by an outer surface composed of a plurality of flat sides 5 which intersect each other to form a plurality of longitudinally extending corners 6.

The elongated body 1 has a front portion 7 of generally pyramidal shape at the front of the intermediate portion 4. The front portion 7 includes an axially aligned tip or point 8 and a plurality of faces 9 which correspond in number to the number of sides 5 on the intermediate portion 4. The faces 9 diverge rearwardly from the tip 8 along curves which smoothly blend or join with the longitudinal sides of the intermediate portion so that the faces 9 are, in effect, smooth continuations of the sides 5 terminating at the tip 8. The pyramidal shaped front portion 7 further includes corners 10 which extend continuously from the tip 8 rearwardly along diverging and inwardly curved lines to smoothly blend with the corners 6 of the intermediate portion 4. This blending of the faces 9 with the sides 5 and the corners 10 with the corners 6 is the natural result of the method of manufacturing the moil point 1.

The faces 9 are concave in transverse section as they extend rearward from the tip 8. The concave curvature of the faces 9 is greatest near the tip 8 and becomes progressively less as they extend rearward. The 'faces 9 become substantially fiat in cross section as they join the sides 5 of the intermediate portion 4.

The faces 9 cooperate with the sides 5 to form smooth paths or troughs for conveying the dust and cuttings from the tip 8 rearwardly. Each of these troughs or paths is bordered by a pair of the corners 6 and 10. Since these troughs are continuous and do not have any discontinuities, the dust and cuttings do not tend to accumulate and pack up" at any place along their length. This fact is believed to be the reason for the non-sticking ability of this tool. The fact that the troughs are concave may also enhance the non-sticking qualities of the tool.

Method The method of manufacturing the novel tool 1 is illustrated schematically in FIGS. 8 to 10. A tool blank 15 is mounted in a pair of longitudinally spaced holders l6 and 17. The blank 15 is hexagonal in cross section and is provided at its opposite ends with shanks 2 and collars 3, these elements being formed on the blank prior to being mounted in the holders 16 and 17.

The middle of the blank 15 is heated to a predetermined drawing temperature by conventional means, such as the electrical induction heating coil 18 shown in FIG. 8. When using high carbon steel (1% carbon content) as the material for the blank 15, I have found that the predetermined drawing temperature should be in the range of 1,800 to 2,000 degrees F. in order for my method to operate best.

When the middle of the blank 15 reaches the proper temperature, the two holders are pulled away from each other to draw the heated middle of the blank axially apart. FIG. 8 illustrates the blank 15 as its middle is partly drawn or attenuated. The force or load acting to pull the holders l6 and 17 apart may be applied before the blank 15 reaches the proper drawing temperature or it may be applied after the temperature is reached. If the load is applied before the blank 15 reaches the proper temperature, the blank will withstand the load until the proper temperature is reached. Hence, the blank 15 will automatically start drawing when the correct temperature is reached. At any rate, it is important that the blank 15 continue to be heated as it is drawn or attenuated. Otherwise, the blank 15 will break or separate before the pointed ends are properly formed. In using 1% carbon steel for the blank 15, I have found that a satisfactory drawing load on the blank can be in the region of 5,000 p.s.i.

Ultimately, the blank 15 will be drawn down to a very small cross section in its heated portion and will separate into a pair of elongated members having pointed ends formed at the point of blank separation. During the attenuation of the blank 15, the heated portion of the blank will automatically form the sides 5 of the blank into the concave shaped faces 9 terminating at the tip 8 of the front portion 7 of each tool body 1. Once the blank reaches the proper drawing temperature, I have found that the entire drawing operation lasts for about five seconds.

After being formed by the foregoing steps, the rnoil points 1 may be heat treated by conventional methods to harden them before use.

Although a preferred embodiment of the invention is illustrated and described in detail, it will be understood that the invention is not limited simply to this embodiment, but contemplates other embodiments and variations which utilize the concepts and teachings of this invention.

Having described my invention, I claim:

1. A percussively operated tool for drilling and breaking concrete and the like, comprising:

(a) an elongated body including rear, intermediate and front portions;

(b) said rear portion forming a shank adapted to be actuated for operating said tool;

(0) said intermediate portion having a polygonal cross section formed by a plurality of intersecting fiat sides and longitudinally extending parallel corners located at the intersections of the flat sides; and

((1) said front portion having substantially a pyramidal shape including a pointed end adapted to penetrate concrete and the like and a plurality of intersecting faces corresponding in number to the number of flat sides on said intermediate portion, said faces diverging rearwardly outward and smoothly blending at their rear ends with the fiat sides of the intermediate portion to form a plurality of smooth paths extending rearward from said point along said front and intermediate portions for conveying cuttings from said point during the operation of said tool.

2. The tool of claim 1 wherein:

(a) said paths are concave shaped troughs adjacent the pointed end of said front portion.

3. A percussively operated tool for drilling and breaking concrete and the like, comprising:

(a) an elongated body of substantially polygonal cross section and including an intermediate Portion having a plurality of longitudinally extending intersecting sides and a front portion of generally pyramidal shape which attenuates forward from said intermedi ate portion to terminate in a point adapted for drilling and breaking concrete and includes a plurality of longitudinally extending intersecting sides smoothly blending with said sides of said intermediate portion and extending forwardly to said point and defining a plurality of smooth paths extending rearwardly along said front and intermediate portions.

4. The tool of claim 3 wherein:

(a) the longitudinally extending intersecting sides of said front portion form a plurality of longitudinally extending troughs which are concave in cross section and extend rearwardly from said point.

References Cited by the Examiner UNITED STATES PATENTS 1,024,039 4/1912 Steen 40 1,727,752 9/1929 Decker l74-3 l 3 2,161,062 6/1939 Killgore 29994 2,302,069 11/ 1942 Stephens 29994 2,507,817 5/1950 Ropp et al 2197.5 X 2,614,811 10/1952 Melendy 4l4 2,627,315 2/1953 Hettinger 17519 2,688,264 9/1954 Rudquist 76l08 3,011,367 12/1961 Tilden 76l08 FOREIGN PATENTS 562,122 6/1944 Great Britain.

ERNEST R. PURSER, Primary Examiner.

JOHN C. CHRISTIE, CHARLES E. O'CONNELL,

Examiners. J. E. PEELE, Assistant Examiner. 

3. A PERCUSSIVELY OPERATED TOOL FOR DRILLING AND BREAKING CONCRETE AND THE LIKE, COMPRISING: (A) AN ELONGATED BODY OF SUBSTANTIALLY POLYGONAL CROSS SECTION AND INCLUDING AN INTERMEDIATE PORTION HAVING A PLURALITY OF LONGITUDINALLY EXTENDING INTERSECTING SIDES AND A FRONT PORTION OF GENERALLY PYRAMIDAL SHAPE WHICH ATTENUATES FORWARD FROM SAID INTERMEDIATE PORTION TO TERMINATE IN A POINT ADAPTED FOR DRILLING AND BREAKING CONCRETE AND INCLUDES, A PLURALITY OF LONGITUDINALLY EXTENDING INTERSECTING SIDES SMOOTHLY BLENDING WITH SAID SIDES OF SAID INTERMEDIATE PORTION AND EXTENDING FORWARDLY TO SAID POINT AND DEFINING A PLURALITY OF SMOOTH PATHS EXTENDING REARWARDLY ALONG SAID FRONT AND INTERMEDIATE PORTIONS. 